Alfalfa/Grass Mixtures vs. Alfalfa: Profitable Alternatives to Deter the Potato
Leafhopper
Principal Investigators:
Roger Bender, Shelby Co.
Mark Sulc, Horticulture & Crop Science
Jim Jasinski, SWD, IPM Specialist
Harold Willson, Entomology
Abstract:
A field research project, to compare the effect of alfalfa/grass mixtures with pure alfalfa
stands, on potato leafhopper populations, was planted August 16, 1993. Comparisons included a
standard alfalfa variety (Provico) with 1 lb. of orchardgrass and with 2 lbs. of orchardgrass, standard
alfalfa alone (control), and a reputed potato leafhopper resistant alfalfa variety (ABI 9045). These 4
plantings were randomly replicated 4 times for a total of 16 plots. The soil was tilled twice to level
the seedbed, kill existing weeds and volunteer wheat, and to incorporate fertilizer. An excellent stand
was established, despite very dry conditions 2 weeks after the planting date. The alfalfa stand survived
the winter and comparison of the plots with PLH populations, yield and palatability records gathered
for 2nd and 3rd cuttings. The research project is planned for a 3- to 5-year period, depending on the
vitality of the stand. The orchardgrass seedings did not survive, so timothy was planted in September
following the original grass plot layout. Thus, comparative mixtures could not be analyzed in 1994.
The plots are on land involved in the Lake Loramie Water Quality Incentive Project (WQIP) and could
result in reduced insecticide use. One acre replicated plots to compare infestations of PLH have been
planted. Large plots are critical to accurately assess the impact of control strategies on PLH
populations because of their mobility.
To evaluate potential PLH tolerance or resistance in variety ABI 9045, half of the plots of
each variety were treated with an insecticide during the 2nd and 3rd cuttings and half remained
untreated on the assumption that any differences in PLH impact between treated and untreated plots
would be less in the tolerant variety than a susceptible variety. Following treatments, relative PLH
abundance was monitored, pre-harvest stand height was measured, yields were determined, and harvest
samples were evaluated for differences in forage quality.
Significant reductions in leafhopper activity and associated impact on stand height were
observed between treated and untreated plots of both varieties (see Table 1). However, no significant
differences were observed between varieties. If variety ABI 9045 was tolerant or resistant to
leafhopper, the untreated plots of ABI 9045 should have demonstrated relatively less reduction in
stand height compared to that of the Provico variety which is presumed to be susceptible to leafhopper
impact. No significant differences were observed among yields and differences in forage quality were
minimal (see Tables 2 & 3).
For further information contact Roger Bender , Extension Agent, Ohio State University Extension, Shelby County or the Ohio IPM Office.
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